Me and my mates was on Specials Ops last night for a considerable amount of time
you have to earn Stars to unlock the next levels and you only get 1 star for easy so that isn't enough so we went on Veteran for 3 and it is awesome
One took us 35 minutes (est completion time was 5) and that was to clear just 5 waves of people and vehicles but after 2 we got pushed in and ended up having to hide behind counters in the diner

God knows how you would do any of these alone
The single player side is worth £40 imo as it is just like a film you play in and has alot of surprises with you involved and some great twists in the story. Its the best single player game i have played in a long time, its even just watchable as some games are without getting bored
If you dont get this your missing out on what could be GOTY, simple as that really
Oh and its £40 here where i ordered
http://www.coolshop.co.uk/catalog/product/58724-modern-warfare-2-(call-of-duty)--for-x360